This Video Explains How Your Body Is Evidence That Evolution Is Real

Our minds are blown.

A new video from Vox shows you exactly why unused vestigial organs and functions, such as goosebumps, are evidence of evolution — and it’s fascinating. The video calls them "evolution's leftovers," and shows how these body parts and functions have outlived their original contexts.

The video points out how all of us can find evidence of evolution in our bodies, like the unnecessary presence of the palmaris longus, a tendon between the arm and hand that’s missing in roughly 10 to 15% of humans with no repercussions.

The palmaris longus looks like a vein — the video shows you how to check for its presence by holding your arm to a hard surface and watching it pop up — but it doesn’t really do much for humans. It was originally present in animals that used their arms for mobility, and remains in humans and closer primates, like apes and gorillas, as essentially a souvenir from our earlier forms. Other examples include goosebumps, which are useless for us but help furrier mammals control body heat, and tailbones, which are attached to actual tails in the human gestation period, though the tails usually disappear a few weeks later.